Few motorists spend time wondering what ingredients went into making the asphalt that helps their tires to grip the road.

Dale Behnen, co-owner of Peerless Landfill Inc. near Valley Park, is a notable exception. She has led a crusade to change the asphalt-road recipe, making it better for the environment.

The key ingredients in Behnen's plan are shingles torn from roofs.

And in a few months, her efforts could culminate with a significant change in road construction in Missouri.

Each year, Peerless, a construction and demolition landfill, receives about 25,000 to 30,000 tons of shingles, all of which are buried.

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Most shingles, like asphalt, are a petroleum-based product. Rather than dump old shingles into landfills, Behnen reasoned, why not grind them up and put them into the asphalt-road mix?

The idea isn't novel. Several states allow road asphalt to include a mix of 5 percent to 10 percent of the shingles scrapped by manufacturers.

"It's a good product," said Timothy Townsend, a professor of environmental engineering at the University of Florida and an expert in shingle recycling.

Furthermore, he said, putting cast-off shingles into asphalt roads "provides a way to re-use material that might otherwise end up in a landfill."

Minnesota is among the heaviest users of recycled scrap asphalt. Statewide, about 12,000 tons of asphalt shingles make their way annually into state and local roads, said Roger Olson, a research operations engineer for the Minnesota Department of Transportation.

Even so, Behnen's plan doesn't involve scrap shingles, which are never used and, therefore, relatively clean. She wants to use weathered shingles torn from roofs.

There's one big drawback: Tear-off shingles include a high volume of contaminants, which highway engineers call deleterious materials. These can include asbestos and nails and wood, all of which can compromise the integrity of the asphalt mix and roads.

"It's garbage in and garbage out," Townsend said.

That's why Minnesota doesn't allow tear-off shingles to be used in asphalt.

In theory, every bit of unwanted stuff can be removed from tear-off shingles. But reaching perfection would require teams of workers and loads of expensive equipment, making an asphalt road only slightly less expensive than a gold-plated highway.

Behnen enlisted the help of Pace Construction Co. of south St. Louis County, a road builder that coincidentally had been looking at tear-off shingles, too.

Pace and Peerless have been working on a mix that contains some contaminants without sacrificing road quality.

"The biggest problem we get with deleterious material is wood," said Roger Brown, vice president at Pace.

Unlike nails, wood cannot be extracted by magnets. And unlike plastic, it doesn't melt during the asphalt-mixing process.

Despite the challenge, Pace has come up with a mix that has held up in lab tests. This month, the mix was used to construct a half-mile private road for trucks at a quarry near Eureka.

Missouri highway officials believe that it's not only the first road in the state with a mix of tear-off shingles but also one of the first in the nation.

Brown is certain that the road will last, but he and Behnen need to convince the Missouri Department of Transportation. The agency's regulations apply only to state highway projects, but counties and local governments tend to adopt the same standards.

In short, if MoDOT doesn't sign off, the shingles probably will be buried.

The state's standards allow virtually no contaminants, said Joe Schroer, field-materials engineer for the agency. But he and others are studying the Eureka road closely, checking for abnormal weathering, pavement separation or cracking.

"Within the next several weeks, we should be able to decide what direction we want to take this," Schroer said. "From our standpoint, we would still like to see those foreign materials limited."

Behnen is hopeful that MoDOT will loosen its standard on deleterious materials. She has invested heavily in processing and grinding equipment, relying in part on grants from the St. Louis-Jefferson Solid Waste Management District.

"Our mission is to reduce the amount of waste being generated for disposal," said Dave Berger, executive director of the district. "A significant amount of waste is being generated by shingles." Berger credits Behnen with getting MoDOT's attention on recycled shingles.

"If it wasn't for Dale's persistence, we wouldn't be here," he said. "Dale really did the heavy lifting to get this to come together."

Even if Behnen gets MoDOT's endorsement, she still has an uphill battle. The economics of using recycled shingles remain uncertain.

Pace probably would avoid using tear-off shingles if it didn't lead to equal or lower asphalt prices, Brown said.

"We'd like to be benevolent and help the environment, but it really makes it attractive if you can make some money on it," Brown said.

For her part, Behnen acknowledges that she doesn't know where things will go with recycled shingles. "We're all inventing the wheel."

But she allows for the possibility that a half-mile quarry road represents the first small move toward much wider acceptance.

"We know how to grind it. We know how to screen it. We know how to stockpile it," she said. "Right now, we need the markets."